Integrated Circuit (IC) Fabrication MCQ [Free PDF] - Objective Question Answer for IC Fabrication Quiz

41. The process involved in photolithography is

A. Making of a photographic mask only
B. Photo etching
C. Both photo etching and the making of the photographic mask
D. None of the mentioned

Answer: C

Photolithography involves both processes in sequence. The first photographic mask is used for artwork and reduction. Then Photo etching for removal of SiO₂ from the designed region.

42. How will be the initial artwork done for a normal IC?

A. Smaller than the final dimension of chip
B. Same as that of final dimension of chip
C. Larger than the final dimension of chip
D. None of the mentioned

Answer: C

The initial artwork of an IC is done at a scale several hundred times longer than the final dimensions. This is because, for a tiny chip, the larger the artwork, the more accurate is the final mask.

43. Find the area of artwork done for a monolithic chip of area 30mil × 30mil.

A. 16 cm × 16 cm
B. 60 cm × 60 cm
C. 12 cm × 12 cm
D. 36 cm × 36 cm

Answer: D

Drawings are magnified by a factor 500.

=> 1mil = 25µm

Therefore, 500mil = 1.2cm.

In an area of 30mil × 30mil, the area for artwork required

= 30mil × 1.2cm = 36cm × 36cm.

44. Mylar coated with a sheet of red photographic Mylar is used for artwork (layout) because

A. It is used to get a colorful layout
B. It can be easily peeled off from the layout
C. It is recommended color for layouts
D. It is used for highlighting layout

Answer: B

For photographic purposes, artwork should not contain any line drawing but must be of alternate clear and opaque regions.

The red layer can be easily peeled off thus exposing clear areas with a knife-edge from regions where impurities have to be diffused.

45. Find the coating material used for the photo etching process along with its thickness range.

A. Kodak photoresist (5000-10000Å)
B. Kodak photoresist (1000-5000Å)
C. Kodak photo etchant (1000-5000 Å)
D. Kodak photo etchant (500-1000 Å)

Answer: A

The coating material is Kodak photoresist. It is a photosensitive emulsion film coated on the wafer to remove SiO₂ from the desired region.

46. Which type of etching process is preferred to make the photoresist immune to etchants?

A. None of the mentioned
B. Wet etching
C. Plasma etching
D. Chemical etching

Answer: C

Plasma etching is also called dry etching. The major advantage of the dry etching process is that it is possible to achieve smaller line openings (<1µm) compared to other processes.

47. Which of the following statement is not true?

A. X-ray and Electron beam lithography technique, produce device dimensions down to the submicron range.

B. Ultraviolet lithography has limitations due to diffraction effects of wavelength.

C. The cost of X-ray or Electron beam is less compared to Ultraviolet photolithography.

D. The exposure time is less in Ultraviolet compared to X-ray or Electron beam lithography.

Answer: C

The cost of an X-ray or Electron beam is very high and thus, it is an expensive process. Therefore, it is used only when very small device dimensions (<1 µm) are needed.

48. For photographic purposes usually coordinate graph is preferred for artwork because

A. It is a precision drafting machine
B. Cutting head can be positioned accurately
C. It can be moved along two perpendicular axes
D. All of the mentioned

Answer: D

A coordinate graph is a drafting machine that outlines the pattern cutting through the red Mylar without damaging the clear layer underneath.

49. Which of the following is added as an impurity to p-type material in the diffusion process?

A. Phosphorous pentaoxide (P₂O₅)
B. Phosphorous oxychloride (POcl₃)
C. Boron oxide (B₂O₃)
D. None of the mentioned

Answer: C

Boron oxide (B₂O₃) is added as an impurity to p-type material in the diffusion process.

Boron is a p-type material, whereas Phosphorous is an n-type material.

50. In the fabrication of monolithic ICs, Boron chloride is added as an impurity in the diffusion process. Find the diffusion time, if the furnace is heated up to 1200°c.

A. 1 hour
B. 2 hours
C. 45 minutes
D. 30 minutes

Answer: B

In the diffusion process, the depth of diffusion of impurities depends upon the time taken for diffusion, which normally extends for more than 2 hours.

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